The object of this research is to understand the role of specific lesions in DNA in effecting cell death. Using antiserum made against UV-irradiated DNA, we have developed a radioimmunoassay capable of detecting photoproducts in the DNA of mammalian cells at biologically relevant dose levels. Depending on the assay conditions, this antiserum can be used to quantify both cyclobutane dimers and Pyr(6-4)Pyo adducts. We now propose to make monoclonal antibodies in order to increase the variety of photoproducts that can be assazed and to analyse intermediary structures formed during DNA repair. The ability of UV-hypersensitive mammalian cell lines to repair various DNA photoproducts will be determined and, using different complementation groups, common repair pathways for different lesions sought. The use of modified UV-DNA/polynucleotides to screen the hybridomas will enable us to isolate potential probes for the analysis of the DNA repair process. The ability to identify intermediate structures will also assist us in elucidating the defect in the mutant cell lines.